Effects of Nonpoint Source Pollution
The effects of nonpoint source pollution varies according to the specific
pollutant. The examples given below are not an exhaustive list; more examples
can be found on the Louisiana
Nonpoint Source Pollution Program web site.
- Run-off from erosion-prone areas (such as constructions sites and
poorly-managed agricultural lands) can deposit excess amounts of sediment
into nearby receiving water, reducing the clarity of water. Cloudy water
limits the ability of plants to produce oxygen, consequently impacting
fish and other local wildlife. Sediment can also smother lake and ocean
bottom organisms. When sediment fills in waterways, it hinders navigation
and increases flooding.
- Fertilizers washed away from agriculture lands and residential areas
can cause algal blooms in ponds, lakes, and other bodies of water. This
removes oxygen from the water, vastly reducing local populations of
fish. Excess nutrients cause excessive plant growth, disrupting natural
nutrient cycles, again resulting in a decline in the number of desirable
- Improperly managed animal wastes from livestock and improperly-sited
septic tank systems can produce dangerously high levels of fecal coliform
bacteria and other harmful microorganisms. This can lead to diseases
such as infectious hepatitis, typhoid fever, dysentery, and other forms
of diarrhea, rendering streams, rivers, bayous, lakes, and other bodies
of water unfit for human use (such as fishing, swimming, water skiing,
- Crop debris is a major organic pollutant resulting from agricultural
activities. During decomposition, it removes oxygen from receiving waters
which can result in stress or death among fish and other aquatic species.
- Herbicides, pesticides, and other toxic agents that have been washed
into rivers, streams, lakes, bayous, and other bodies of water can collect
in local plants and animals. As a result, local wildlife becomes unfit
for human consumption, which reduces opportunities for hunting and fishing.
In addition, soluble pesticides and herbicides can reach ground water,
rendering it unsafe for drinking or necessitating expensive cleanup.
- Chemicals (including excessive concentrations of salts and minerals),
petroleum products, and heavy metals all contaminate receiving water,
rendering water unfit for human and animal consumption and impairing
the growth of plants. It can also reduce or restrict the water's value
for industrial and municipal use, irrigation, and propagation of fish
and wildlife. Water purification and treatment systems become more expensive
to operate. Excessive salts can adversely alter the permeability of
- Louisiana's coastal marshlands are some of the most productive soil,
water, and plant resources existing in the United States of America.
However, saltwater intrusion converts approximately 88 acres (356,136
square meters) of marshlands to open water each day. This annual loss
of 32,000 acres (129.5 square kilometers) of marshland accelerates each
year. Intrusion of saltwater causes the loss of fresh and intermediate
vegetation, which results in rapid erosion of marsh soils and the ultimate
conversion to open water.